R. Dallier

Radio-detection signature of high-energy cosmic rays by the CODALEMA experiment

Taking advantage of recent technical progress which has overcome some of the difficulties encountered in the 1960’s in the radio detection of extensive air showers induced by ultra high energy cosmic rays (UHECR), a new experimental apparatus (CODALEMA) has been built and operated. We will present the characteristics of this device and the analysis techniques that have been developed for observing electrical transients associated with cosmic rays. We find a collection of events for which both time and arrival direction coincidences between particle and radio signals are observed. The counting rate corresponds to shower energies ≥ 5 × 10 16 eV. The performance level which has been reached considerably enlarges the perspectives for studying UHECR events using radio detection.

Geomagnetic origin of the radio emission from cosmic ray induced air showers observed by CODALEMA

The new setup of the CODALEMA experiment installed at the Radio Observatory in Nancay, France, is described. It includes broadband active dipole antennas and an extended and upgraded particle detector array. The latter gives access to the air shower energy, allowing us to compute the efficiency of the radio array as a function of energy. We also observe a large asymmetry in counting rates between showers coming from the North and the South in spite of the symmetry of the detector. The observed asymmetry can be interpreted as a signature of the geomagnetic origin of the air shower radio emission. A simple linear dependence of the electric field with respect to ∧ is used which reproduces the angular dependencies of the number of radio events and their electric polarity.

Radio detection of cosmic ray air showers by the CODALEMA experiment

The possibilities of measuring Extremely High Energy Cosmic Rays (EHECR) by radio detection of electromagnetic pulses radiated during the development of extensive air showers in the atmosphere are investigated. We present the demonstrative CODALEMA experiment, set up at Nancay Radio-Observatory (France). The radio-decametric array has been adapted to measure radio transients in time coincidence between antennas.

Radiodetection of Cosmic Ray Extensive Air Showers: upgrade of the CODALEMA experiment

We present the characteristics and performance of a demonstration experiment devoted to the observation of ultra high- energy cosmic ray extensive air showers using a radiodetection technique. In a first step, one antenna narrowed band filtered acting as trigger, with a 4 sigma threshold above sky background-level, was used to tag any radio transient in coincidence on the antenna array. Recently, the addition of 4 particle detectors has allowed us to observe cosmic ray events in coincidence with antennas.

CODALEMA: A COSMIC RAY AIR SHOWER RADIO DETECTION EXPERIMENT

The CODALEMA experimental device currently detects and characterizes the radio contribution of cosmic ray air showers : arrival directions and electric field topologies of radio transient signals associated to cosmic rays are extracted from the antenna signals. The measured rate, about 1 event per day, corresponds to an energy threshold around 5.1016eV. These results allow to determine the perspectives offered by the present experimental design for radiodetection of Ultra High Energy Cosmic Rays at a larger scale.

Noncooled near-infrared spectroscopy

We investigate the use of non-cryogenic instrumentation for near IR spectroscopy. With this technique, it is possible to apply in the J and H bands some instrument concepts and observing techniques used in the visible. We present observations of the thermal background in H. We derive some instrument requirements for minimizing and handling it. We recommend the use of short wavelength cutoff wavelengths or linear filters in H. We present observations of the sky emission, and do confirm previous upper limits of the continuum emission between the OH lines. We discuss some applications of non-cooled near IR spectroscopy.

ISIS IR: The first infrared fibre-fed spectrograph

ISIS IR is the first attempt to use fibre optics for near infrared spectroscopy (λ≤1.8μm). It is a field spectrograph (2D spectroscopy), and can work at various resolving powers (up to 25000). It can be transported anywhere, and soon it will be used at CFHT with one NICMOS 3-based camera.

Multi-scale and multi-frequency studies of cosmic ray air shower radio signals at the CODALEMA site

Since 2003, the Nancay Radio Observatory hosts the CODALEMA experiment, dedicated to the radio detection of cosmic ray induced extensive air showers. After several instrumental upgrades, nCODALEMA is now composed of: n- 57 self-triggering radio detection stations working in the [20-200] MHz band, over 1 km2; n- an array of 13 scintillators acting as a particle detector; n- a compact array of 10 cabled antennas, triggered by the particle detector, to test the capabilities nof a phased antenna cluster to cleverly select air shower events. nIn addition, CODALEMA supports the EXTASIS project, aiming at detecting the expected lowfrequency signal produced by the sudden deceleration of the air shower particles hitting the ground. Beside these dedicated arrays, the Nancay site will host the NenuFAR radio telescope (recognized as a SKA pathfinder), made of 1824 dual crossed-polarization antennas similar to the CODALEMA ones. All these arrays present different antenna density and extent, and could be operated in a joint mode to record simultaneously the radio signal coming from an air shower. nTherefore, the upgraded CODALEMA facilities could offer a complete description of the air shower induced electric field at small, medium and large scale, and over an unique and very wide frequency band (from ~ 2 to ~ 200 MHz). The use of multi-band detectors combined with composite ntrigger algorithms could help boosting the radio detection technique as a candidate for an accurate composition measurement with a high efficiency, or in the frame of a further very large cosmic ray observatory. We describe the current and foreseen instrumental set-up together with nthe prospective developments of the radio detection technique.